1. Field of the Invention
The present invention relates to the field of radar fuzes for submunitions, and particularly, to a method and apparatus for a radar fuse employing FM radar.
2. Discussion of the Prior Art
Traditionally, submunition subassemblies are designed to meet specifications requiring low cost and small size. As a result, radar fuzes employed in such submunition subassemblies in the prior art have suffered performance deficiencies.
Typically, in use, up to 30 submunitions are dropped together in close formation. Individual altitude radars within each submunition detect the desired trip point altitude above ground to fuze the submunition. Prior art radars have inaccuracies which may cause the munition to fuze late or prematurely, thereby degrading the effect of the event. Such inaccurate firing may be caused by various factors including mutual interference (i.e. one radar causing another radar to trigger prematurely), errors in detecting range to the launch vehicle, after release, instead of the ground, detecting and tripping on slant range return instead of the correct straight down return during extreme pitch conditions, and detecting ambiguous returns caused by the transmitted modulation technique and inaccuracies caused by analog trip point detection circuits.
The present invention, in contrast to the prior art, provides a unique method of accurately triggering a submunition at complexity and cost levels well below present fuze systems by providing a unique, simple, yet highly effective means of eliminating mutual interference; eliminating false trips due to detection of the launch vehicle; eliminating false altitude trips caused by modulation technique; detecting the nearest edge of the ground return instead of the slant range as detected by prior art devices; and providing automatic calibration of the trip point altitude. These capabilities are provided by a unique digital design mechanized in a single, low cost digital logic circuit.